File:Figure 1a.png

Ground Sampling Distance of drone-based litter surveys. a) Schematic representation of Ground Sampling Distance (GSD) calculation. Following Eq. (1), the collected image is expressed in pixel square, sw indicates the sensor width, f the camera focal length, and H the drone flight height above the ground; b) GSD adopted by drone-based litter surveys found in the literature for different environmental domains and type of litter (blue backgrounds refer to floating litter)